1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a display device which has a liquid crystal display which has a plurality of liquid crystal pixels arranged in a matrix and on which writing is carried out after reset of the liquid crystal.
2. Description of Prior Art
In recent years, liquid crystal displays which use chiral nematic liquid crystal which exhibits a cholesteric phase at room temperature attracts attention because such displays have a memory effect, that is, are capable of displaying an image thereon continuously after the supply of electric power thereto is stopped.
However, in such a liquid crystal display, it is necessary to reset the liquid crystal before writing, and it takes a long time to complete writing. During the writing, in the part on which writing is being carried out, the light absorbing layer provided on the backside of the pixels is seen as black lines (blackout), which raises a problem that the screen is difficult to see.
In portable equipment such as note-type personal computers, mobile telephones, PDA, digital cameras, video cameras, etc., batteries are used as the power sources, and therefore, the available time of such a device after an electric charge thereto is limited. It is demanded to lengthen the available time.
In order to comply with this demand, it is good to use the above-described reflective type liquid crystal displays which have a memory effect and which therefore consume little electric power. This will contribute to energy saving and will never obstacle downsizing, lightening and thinning of the devices. Thus, in the near future, it will be indispensable to employ a reflective type liquid crystal display with a memory effect for portable equipment.
A liquid crystal display with a memory effect consumes electric power while carrying out writing thereon. Therefore, such a liquid crystal display consumes little electric power while displaying a still image continuously but consumes great electric power while writing images repeatedly.
A typical example of liquid crystal with a memory effect is chiral nematic liquid crystal. This kind of liquid crystal takes a longer time for writing thereon than TFT liquid crystal, and this kind of liquid crystal has been considered to be unsuited to display motion pictures and rapidly changeable images (for example, display of inputted letters, scroll of a screen).